Systems which provide location and tracking information have become increasingly significant in modern life. A class of services in this field that is becoming increasingly prevalent is known as Location Based Services. Among these, systems that provide location awareness and tracking of personnel or assets are gaining increasing importance. Such systems are meant to transmit location information of personnel or assets, and to subsequently track the movement of personnel or assets for various applications. A majority of such systems utilize either GPS or terrestrial or satellite signal based receivers to determine the exact of the person or asset. The systems then use either existing cellular infrastructure such as GSM or GPRS, broadband wireless systems such as WiFi or WiMAX, or other wireless techniques to wirelessly transmit the determined location to an interested party.
Location information is of paramount importance in a Safety of Life event. The availability of precise location information enables search and rescue personnel to quickly reach the desired location and then to efficiently conduct rescue operations. Such precise location information is extremely important, for example, in rescue at sea operations, where multiple targets are dispersed over a large body of water, and where the likelihood of survival is significantly dependent on the elapsed time between the catastrophic event and the rescue of the survivors.
Known systems for Safety of Life at Sea procedures operate in specific frequency channels within the HF, VHF and UHF bands. Emergency Position Indicating Radio Beacons (EPIRB), VHF Radios, HF radios and various other systems are used for sending and receiving distress signals in the event that assets or personnel are in distress. Additionally, beacons signals operating in VHF frequencies are used to aid the rescue team in accurately homing on to and locating the survivors.
One of the drawbacks of the known systems is that the number of simultaneous users is limited, due to the narrow frequency spectrum available for use by the system. As a result, in situations having a large number of persons in distress, co-channel interference may occur, wherein the signals from each user will interfere with each other due to all the signals occupying the same frequency band. The known systems do not provide any sort of time, frequency, or any other type of multiplexing, which is necessary when multiple users are using the same spectrum. Due to the narrow spectrum and to the lack of multiplexing, the known Safety of Life at Sea systems are ineffective in situations having a large number of survivors dispersed over an area.
For example, in a situation where an airliner is forced to make a water landing, or a catastrophic event on a drilling rig, several hundred people may be dispersed in the water surrounding the ditch site. In the event of a marine vessel accident, the number of people to be rescued may be in the thousands. In such situations, the Emergency Location Transmitter (ELT) may be able to transmit information as to the location of the incident to the rescue team. However, by the time the rescue personnel arrive, the survivors may have drifted and become scattered across a large area. Rescue of the survivors depends firstly on locating the persons who might have drifted long distance from the crash or evacuation site. An electronic tracking and homing system which is attached to each individual, for example to the individual's the life jacket or personal floating device (PFD) can be of significant help in the locating survivors.
However, in the situations highlighted above, and in similar situations where a large number of survivors need to be located simultaneously, the existing Safety of Life systems are not satisfactory for locating and tracking a large number of personnel. Accordingly, there is a need for a location and tracking system that is able to locate and track a large number of individuals simultaneously in the area of a catastrophic event.